System of electrical distribution.



No. 7|0,l58. Patented Sept. 30, I902.

Y B. G. LAMME.

SYSTEM OF ELECTRICAL DISTRIBUTION.

(Application filed Oct. 14, 1901. (lo Ilodel.)

mmssszs v [NYE/(70R $55M 55mm W P I UNITED STATES PATENT OEEIcE.

BENJAMIN G. LAMME, OF PITTSBURG, PENNSYLVANIA, ASSIGNOR TO IVESTINGHOUSE ELECTRIC (it MANUFACTURING COMPANY, A COR- PORATION OF PENNSYLVANIA.

SYSTEM OF ELECTRICAL DISTRIBUTION.

SPECIFICATION forming part of Letters Patent N 0. 710,158, dated. September 30, 1902. Application filed October 14,1901. Serial No. 78,588- (No model To all whom it may concern:

Be it known that I, BENJAMIN G. LAnME, a citizen of the United States, residing at Pittsburg, in the county of Allegheny and State of Pennsylvania, have invented new and useful Improvements in Systems of Electrical Distribution, of which the following is a specification.

My invention relates to systems of electrical distribution, and particularly to such systems as involve the conversion of alternating-current energy into direct-current energy by means of rotary converters.

The object of my invention is to provide a simple and efficient means for starting rotary converters by means of direct-current energy the voltage of which is less than the normal voltage of the system to be supplied by the machines, but which is more than one-half such voltage.

Since rotary converters which are utilized for converting alternatin current energy into direct-current energy are, in eifect, synchronous motors, some special means must be employed for bringing them up to approximately synchronous speed before they are connected to the alternating-current circuit in connection with which they are used.

In the operation of a plurality of rotary converters in parallel it is important that each converter which is to be connected in circuit with one or more which are already in operation should be so connected without an excessive rush of current from either the alternating-current system to the direct-current system, or vice versa. In case the starting-current is supplied at. an approximately constant electromotive force and such elec tromotive force is higher than the normal electromotive force of the rotary converter the desired condition may be brought about by inserting a suitable resistance between the direct-current source of energy and the commutator of the converter. If, however,

the direct-current-supply voltage is lower than the normal voltage of the rotary converter, the insertion of resistance to prevent a rush of current from the alternatingcurrent circuit to the direct-current circuit will prevent the rotary converter from attaining to the desired voltage and speed. It follows, therefore, that under the last-mentioned relation of voltages the parallel connection must be made when there is a considerable difference between the alternating-current voltage of the rotary converter and that of the system unless some other method of utilizing the low voltage be employed.

IVhere a considerable number of rotary converters are employed in a single system, they may be and ordinarily are located in substations that are a considerable distance apart, and it may happen that when it is necessary to start one of the rotary converters in a given substation the direct-current electromotive force in the main direct-current circuit is at this point materially below the normal eleotromotive force of the system. By utilizing my present invention this relatively low electromotive force may be employed for starting any rotary converter and bringing it to synchronous speed before it is connected to the alternating-current circuit, provided the supply-voltage is more than half the normal voltage of the rotary converter.

My invention is illustrated in the accompanying drawing, the single figure of which is a diagram embodying an alternating-current circuit, a direct-current circuit, and a plurality of rotary converters and cooperating devices.

I have shown in the drawing three rotary converters 1, 2, and 3 for receiving energyin parallel from a three-phase alternating-current circuit 4: 5 6 and supplying direct-current energy in parallel to a direct-current circuit 7 8. My invention is, however, not limited to the employment of any specific number of rotary converters or to a threephase alternating current supply circuit. Each of the rotary converters is also shown as provided with a shunt field-magnet winding 9 and with a regulating-rheostat 10 in circuit therewith, it being understood, however, that my invention is not dependent upon or limited to the employment of this specific type of field-magnet winding.

The alternating-current ends of the rotary converters 1, 2, and 3 are connected to and disconnected from the alternating-current circuit 4 5 6 by means of suitable switches 11, the three switches for each machine being preferably suitably connected, so that they maybe operated simultaneously. The dirent-current end of each rotary converter is connected to the direct-current circuit 7 8, which in this instance is shown as supplying the current for starting the rotary converters and bringing them up to synchronous speed by means of conductors 12 and 13 and a switch 14 between the line conductors 7 and one brush of the commutator l5 and by conductors 16 and 17, a variable resistance 18, and a switch-arm 19 between the line conductor 8 and the other brush of the commutator 15.

In order to provide the desired voltage for bringing the rotary converter to synchronism before throwing the switches 11 to circuitclosing position, I provide star-connected balancing-coils 20, the outer ends of which are connected to the collector-rings 21 of the rotary converter by means of switches 22, which are preferably connected, so as to be thrown simultaneously both to open and to close the circuit. To the common terminalof the coils 20 is connected one end of a conductor 25, the other terminal of which is a contact-piece 26 in position to be engaged by the switch-arm 14 when properly manipulated for that purpose.

The rotary converter 1 and the cooperating devices are indicated in proper relations for starting the rotary converter from a state of rest, the switches 11 and 22 being open and the rotary converter being connected across the circuit 7 8 when the resistance 18 is in circuit. This relation of parts is provided in order that the armature of the rotary converter may be caused to generate the small electromotive force necessary to make the autotransformer and its circuit connections effective in the operation of bringing the retary converter to synchronous speed and voltage. As soon as a slow rate of rotation is obtain ed by reason of the connections shown the switches 14 and 22 may be thrown to the positions indicated in connection with the rotary converter 2, the connections being such, as will be readily seen, that one-half of the armature-winding is in service, and consequently the conditions for one-half the normal voltage of the rotary converter will be secured. Since the resistance 18 is connected in circuit when this change is made, there is no difficulty experienced in making the transfer from full voltage to half-voltage. \Vhen this condition is reached, the resistance 18 can be gradually cut out of circuit by moving the switch-arm-l9, and the field-magnet voltage may be adjusted, by means of the rheostat 10, until the rotary converter reaches synchronous speed. hen this speed is attained, the switch 22 will be opened, the switch-arm 14 thrown to the position indicated in connection with rotary converters 1 and 3, and the switch 11 closed, the operative condition of the rotary converterin which it is supplying energy from the alternatingcurrentsystem 4 5 6 to the direct-current system. 7 8 being indicated by the rotary converter 3 and the apparatus connected therewith.

It will be understood without specific illustration that the controlling devices 14, 18, 19, 20, and 22 may, if desired, be embodied in a single apparatus, so that the operation of the controllerhandle may serve to make and break the several circuits in the order above enumerated, this arrangement ofcircuit-controlling devices being within the province of those skilled in the art. It will be also understood that the direct-current energy for starting the rotary converters may be supplied from any suitable source other than that indicated, if desired.

As has already been indicated, my invention is not limited to specific structural details or to special manipulation of the devices employed, except in so far as limitations may be imposed by the state of the art and expressly set forth in the claims.

I claim as my invention- 1. The combination with a rotary converter and a source of direct-current electromotive force, of a plurality of star-connected balancing-coils, means for making and breaking connection between the outer terminals of said coils and the alternating-current end of the rotary converter and means for making and breaking connection between the common terminal of said coils and one side of the source of direct current.

2. The combination with a rotary converter and a source of direct-current electromotive force, of a variable resistance between the rotary-converter armature and one side of said source, a plurality of star-connected balancing-coils, means for makingand breaking connections between the outer terminals of said coils and the alternating-current end of the rotary converter and means for mak ing and breaking connection between one side of the source of direct current and one of the rotary-converter brushes and between said source and the common terminal of the balancing-coils.

3. The combination with a rotary converter and a source of direct-current electromotive force, of a plurality of star-connected balancing-coils, a variable resistance and means for making half-voltage connections between the armature-Winding of the rotary converter and the source of direct-current electromotive force, through the balancing-coils andthe variable resistance, to bring the rotary converter to synchronous speed and voltage.

4. The combination with a rotary converter and a source of approximately constant direct-current electromotive force, of a plurality of star-connected balancing-coils, a variable resistance, means for making and breaking connection between the outer terminals of the balancing-coils and the alternating-current end of the rotary converter and means for making and breaking connection between the common terminal of the balancing-coils and the source of direct-current electromotive force.

5. In a system of electrical distribution, the combination of an alternating-current-supply circuit and a direct-current-distributing circuit, of a plurality of rotary converters for transferring energy from the alternating-current circuit to the direct-current circuit and means for utilizing an electromotive force from the direct-current circuit that is less than the normal voltage of the rotary converters for bringing them to synchronous speed and voltage.

6. In a system of electrical distribution, the combination with an altern ating-current-su pply circuit and a direct-current-distributing circuit, of a plurality of rotary converters for transferring energy from the alternating-current circuit to the direct-current circuit, a balancing device and a variable resistance for each rotary converter and means for connecting each rotary converter to the directcurrent circuit through the balancing device so as to raise the converter to synchronous speed and voltage bydirect-current voltage that is approximately one-half the normal voltage of the rotary converter.

'7. In a system of electrical distribution, the combination with an altern ating-current-supply circuit and a direct=current-distributing circuit, of a plurality of rotary converters for transferring energy from the alternating-current to the direct-current circuit, means for making and breaking connection between the alternating-current circuit and each of the rotary converters and means for supplying, to each rotary converter, direct-current electromotive force of approximately one-half the value of its normal electromotive force to raise the rotary converter to synchronous speed and voltage.

8. A rotary converter for converting alternating-current energy into direct-current energy, in combination with means for supplying direct-current energy to the commutator of said converter at less than the normal voltage of the latter and a balancing device having star connections with the alternatingcurrent end of the converter and having a common terminal connection with the directcurrent-supply circuit.

9. A rotary converter for converting alternating-current energy into direct-current energy, in combination with means for supplying direct-current energy to the commutator of the converter at less than the normal voltage of the converter, a variable resistance in said direct-current-supply circuit and a balancing device havingstarconnections with the alternating-current end of the converter and having its common terminal connected to the direct-current-supply circuit.

In testimony whereof I have hereunto sub= scribed my name this 0th day of October, 1901.

BENJ. G. LAMME.

' Witnesses:

WESLEY G. CARR, BIRNEY I'IINES. 

